Method and apparatus for performing communication in wireless communication system

ABSTRACT

Methods and apparatuses for performing communication in a wireless communication system. A user equipment (UE) receives first satellite ephemeris information related to a first satellite and information related to a first validity duration corresponding to the first satellite from a base station; and restarts a first validity timer, based on second satellite ephemeris information related to the first satellite being received from the base station while the first validity timer having the first validity duration is running. The UE obtains a first TA for the first satellite based on the first satellite ephemeris information before the first validity timer restarts, expires, or stops after starting based on the first validity duration, and the UE obtains a second TA for the first satellite based on the second satellite ephemeris information before the first validity timer expires or stops after restarting based on a second validity duration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/713,816, filed on Apr. 5, 2022, which claims the benefit of anearlier filing date and right of priority to Korean Application No.10-2021-0044236, filed on Apr. 5, 2021, Korean Application No.10-2021-0103409, filed on Aug. 5, 2021, and Korean Application No.10-2021-0113480, filed on Aug. 26, 2021, the contents of which are allhereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and an apparatus for performingcommunication in a wireless communication system.

BACKGROUND

A mobile communication system has been developed to provide a voiceservice while guaranteeing mobility of users. However, a mobilecommunication system has extended even to a data service as well as avoice service, and currently, an explosive traffic increase has causedshortage of resources and users have demanded a faster service, so amore advanced mobile communication system has been required.

The requirements of a next-generation mobile communication system atlarge should be able to support accommodation of explosive data traffic,a remarkable increase in a transmission rate per user, accommodation ofthe significantly increased number of connected devices, very lowEnd-to-End latency and high energy efficiency. To this end, a variety oftechnologies such as Dual Connectivity, Massive Multiple Input MultipleOutput (Massive MIMO), In-band Full Duplex, Non-Orthogonal MultipleAccess (NOMA), Super wideband Support, Device Networking, etc. have beenresearched.

SUMMARY

A technical object of the present disclosure is to provide a method andan apparatus for performing communication in a wireless communicationsystem.

In addition, an additional technical object of the present disclosure isto provide a method and apparatus for obtaining UE-specific timingadvance (TA) based on satellite ephemeris information in anon-terrestrial network system.

In addition, an additional technical object of the present disclosure isto provide a method and an apparatus for configuring a validity durationfor satellite ephemeris information for obtaining UE-specific TA.

The technical objects to be achieved by the present disclosure are notlimited to the above-described technical objects, and other technicalobjects which are not described herein will be clearly understood bythose skilled in the pertinent art from the following description.

According to embodiment of the present disclosure, a method ofperforming communication by a user equipment (UE) in a wirelesscommunication system may include receiving first satellite ephemerisinformation related to a first satellite and information related to afirst validity duration corresponding to the first satellite from a basestation; and restarting a first validity timer, based on secondsatellite ephemeris information related to the first satellite beingreceived from the base station while the first validity timer having thefirst validity duration is running, and the UE obtains a first timingadvance (TA) for the first satellite based on the first satelliteephemeris information before the first validity timer restarts, expires,or stops after starting based on the first validity duration, and the UEobtains a second TA for the first satellite based on the secondsatellite ephemeris information before the first validity timer expiresor stops after restarting based on a second validity duration.

According to embodiment of the present disclosure, a method ofperforming communication by a base station in a wireless communicationsystem may include transmitting, to a user equipment (UE), firstsatellite ephemeris information related to a first satellite andinformation related to a first validity duration corresponding to thefirst satellite; and transmitting, to the UE, second satellite ephemerisinformation related to the first satellite while a first validity timerhaving the first validity duration is running, and the UE obtains afirst timing advance (TA) for the first satellite based on the firstsatellite ephemeris information before the first validity timerrestarts, expires, or stops after starting based on the first validityduration, and the UE restarts the first validity timer based on thesecond satellite ephemeris information being received, and the UEobtains a second TA for the first satellite based on the secondsatellite ephemeris information before the first validity timer expiresor stops after restarting based on a second validity duration.

According to an embodiment of the present disclosure, a method and anapparatus for performing communication may be provided in a wirelesscommunication system.

According to an embodiment of the present disclosure, a method andapparatus for obtaining UE-specific timing advance (TA) based onsatellite ephemeris information may be provided in a non-terrestrialnetwork system.

According to an embodiment of the present disclosure, a method and anapparatus for configuring a validity duration for satellite ephemerisinformation for obtaining UE-specific TA may be provided.

Effects achievable by the present disclosure are not limited to theabove-described effects, and other effects which are not describedherein may be clearly understood by those skilled in the pertinent artfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Accompanying drawings included as part of detailed description forunderstanding the present disclosure provide embodiments of the presentdisclosure and describe technical features of the present disclosurewith detailed description.

FIG. 1 illustrates a structure of a wireless communication system towhich the present disclosure may be applied.

FIG. 2 illustrates a frame structure in a wireless communication systemto which the present disclosure may be applied.

FIG. 3 illustrates a resource grid in a wireless communication system towhich the present disclosure may be applied.

FIG. 4 illustrates a physical resource block in a wireless communicationsystem to which the present disclosure may be applied.

FIG. 5 illustrates a slot structure in a wireless communication systemto which the present disclosure may be applied.

FIG. 6 illustrates physical channels used in a wireless communicationsystem to which the present disclosure may be applied and a generalsignal transmission and reception method using them.

FIGS. 7A to FIG. 8B are diagrams for describing non-terrestrial network(NTN) supported by a wireless communication system to which the presentdisclosure may be applied.

FIG. 9 is a flowchart illustrating a method of performing communicationby a UE according to an embodiment of the present disclosure.

FIG. 10 is a flowchart illustrating a method of performing communicationby a base station according to an embodiment of the present disclosure.

FIGS. 11A and 11B are diagrams for describing a process of obtaining aUE-specific TA in a wireless communication system to which the presentdisclosure may be applied.

FIG. 12 is a diagram for describing one format of satellite ephemerisinformation according to an embodiment of the present disclosure.

FIG. 13 is a sequence diagram illustrating a signaling procedure betweena UE and a network according to an embodiment of the present disclosure.

FIG. 14 illustrates a block diagram of a wireless communication deviceaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments according to the present disclosure will bedescribed in detail by referring to accompanying drawings. Detaileddescription to be disclosed with accompanying drawings is to describeexemplary embodiments of the present disclosure and is not to representthe only embodiment that the present disclosure may be implemented. Thefollowing detailed description includes specific details to providecomplete understanding of the present disclosure. However, those skilledin the pertinent art knows that the present disclosure may beimplemented without such specific details. In some cases, knownstructures and devices may be omitted or may be shown in a form of ablock diagram based on a core function of each structure and device inorder to prevent a concept of the present disclosure from beingambiguous.

In the present disclosure, when an element is referred to as being“connected”, “combined” or “linked” to another element, it may includean indirect connection relation that yet another element presentstherebetween as well as a direct connection relation. In addition, inthe present disclosure, a term, “include” or “have”, specifies thepresence of a mentioned feature, step, operation, component and/orelement, but it does not exclude the presence or addition of one or moreother features, stages, operations, components, elements and/or theirgroups.

In the present disclosure, a term such as “first”, “second”, etc. isused only to distinguish one element from other element and is not usedto limit elements, and unless otherwise specified, it does not limit anorder or importance, etc. between elements. Accordingly, within a scopeof the present disclosure, a first element in an embodiment may bereferred to as a second element in another embodiment and likewise, asecond element in an embodiment may be referred to as a first element inanother embodiment.

A term used in the present disclosure is to describe a specificembodiment, and is not to limit a claim. As used in a described andattached claim of an embodiment, a singular form is intended to includea plural form, unless the context clearly indicates otherwise. A termused in the present disclosure, “and/or”, may refer to one of relatedenumerated items or it means that it refers to and includes any and allpossible combinations of two or more of them. In addition, “/” betweenwords in the present disclosure has the same meaning as “and/or”, unlessotherwise described.

The present disclosure describes a wireless communication network or awireless communication system, and an operation performed in a wirelesscommunication network may be performed in a process in which a device(e.g., a base station) controlling a corresponding wirelesscommunication network controls a network and transmits or receives asignal, or may be performed in a process in which a terminal associatedto a corresponding wireless network transmits or receives a signal witha network or between terminals.

In the present disclosure, transmitting or receiving a channel includesa meaning of transmitting or receiving information or a signal through acorresponding channel. For example, transmitting a control channel meansthat control information or a control signal is transmitted through acontrol channel. Similarly, transmitting a data channel means that datainformation or a data signal is transmitted through a data channel.

Hereinafter, a downlink (DL) means a communication from a base stationto a terminal and an uplink (UL) means a communication from a terminalto a base station. In a downlink, a transmitter may be part of a basestation and a receiver may be part of a terminal. In an uplink, atransmitter may be part of a terminal and a receiver may be part of abase station. A base station may be expressed as a first communicationdevice and a terminal may be expressed as a second communication device.A base station (BS) may be substituted with a term such as a fixedstation, a Node B, an eNB(evolved-NodeB), a gNB(Next Generation NodeB),a BTS(base transceiver system), an Access Point(AP), a Network(5Gnetwork), an AI(Artificial Intelligence) system/module, an RSU(road sideunit), a robot, a drone(UAV: Unmanned Aerial Vehicle), an AR(AugmentedReality) device, a VR(Virtual Reality) device, etc. In addition, aterminal may be fixed or mobile, and may be substituted with a term suchas a UE(User Equipment), an MS(Mobile Station), a UT(user terminal), anMSS(Mobile Subscriber Station), an SS(Subscriber Station), anAMS(Advanced Mobile Station), a WT(Wireless terminal), anMTC(Machine-Type Communication) device, an M2M(Machine-to-Machine)device, a D2D(Device-to-Device) device, a vehicle, an RSU(road sideunit), a robot, an AI(Artificial Intelligence) module, a drone(UAV:Unmanned Aerial Vehicle), an AR(Augmented Reality) device, a VR(VirtualReality) device, etc.

The following description may be used for a variety of radio accesssystems such as CDMA, FDMA, TDMA, OFDMA, SC-FDMA, etc. CDMA may beimplemented by a wireless technology such as UTRA(Universal TerrestrialRadio Access) or CDMA2000. TDMA may be implemented by a radio technologysuch as GSM(Global System for Mobile communications)/GPRS(General PacketRadio Service)/EDGE(Enhanced Data Rates for GSM Evolution). OFDMA may beimplemented by a radio technology such as IEEE 802.11(Wi-Fi), IEEE802.16(WiMAX), IEEE 802-20, E-UTRA(Evolved UTRA), etc. UTRA is a part ofa UMTS(Universal Mobile Telecommunications System). 3GPP(3rd GenerationPartnership Project) LTE(Long Term Evolution) is a part of anE-UMTS(Evolved UMTS) using E-UTRA and LTE-A(Advanced)/LTE-A pro is anadvanced version of 3GPP LTE. 3GPP NR(New Radio or New Radio AccessTechnology) is an advanced version of 3GPP LTE/LTE-A/LTE-A pro.

To clarify description, it is described based on a 3GPP communicationsystem (e.g., LTE-A, NR), but a technical idea of the present disclosureis not limited thereto. LTE means a technology after 3GPP TS(TechnicalSpecification) 36.xxx Release 8. In detail, an LTE technology in orafter 3GPP TS 36.xxx Release 10 is referred to as LTE-A and an LTEtechnology in or after 3GPP TS 36.xxx Release 13 is referred to as LTE-Apro. 3GPP NR means a technology in or after TS 38.xxx Release 15. LTE/NRmay be referred to as a 3GPP system. “xxx” means a detailed number for astandard document. LTE/NR may be commonly referred to as a 3GPP system.For a background art, a term, an abbreviation, etc. used to describe thepresent disclosure, matters described in a standard document disclosedbefore the present disclosure may be referred to. For example, thefollowing document may be referred to.

For 3GPP LTE, TS 36.211(physical channels and modulation), TS36.212(multiplexing and channel coding), TS 36.213(physical layerprocedures), TS 36.300(overall description), TS 36.331 (radio resourcecontrol) may be referred to.

For 3GPP NR, TS 38.211(physical channels and modulation), TS38.212(multiplexing and channel coding), TS 38.213(physical layerprocedures for control), TS 38.214(physical layer procedures for data),TS 38.300(NR and NG-RAN(New Generation-Radio Access Network) overalldescription), TS 38.331(radio resource control protocol specification)may be referred to.

Abbreviations of terms which may be used in the present disclosure isdefined as follows.

-   -   BM: beam management    -   CQI: Channel Quality Indicator    -   CRI: channel state information-reference signal resource        indicator    -   CSI: channel state information    -   CSI-IM: channel state information-interference measurement    -   CSI-RS: channel state information-reference signal    -   DMRS: demodulation reference signal    -   FDM: frequency division multiplexing    -   FFT: fast Fourier transform    -   IFDMA: interleaved frequency division multiple access    -   IFFT: inverse fast Fourier transform    -   L1-RSRP: Layer 1 reference signal received power    -   L1-RSRQ: Layer 1 reference signal received quality    -   MAC: medium access control    -   NZP: non-zero power    -   OFDM: orthogonal frequency division multiplexing    -   PDCCH: physical downlink control channel    -   PDSCH: physical downlink shared channel    -   PMI: precoding matrix indicator    -   RE: resource element    -   RI: Rank indicator    -   RRC: radio resource control    -   RSSI: received signal strength indicator    -   Rx: Reception    -   QCL: quasi co-location    -   SINR: signal to interference and noise ratio    -   SSB (or SS/PBCH block): Synchronization signal block (including        PSS (primary synchronization signal), SSS (secondary        synchronization signal) and PBCH (physical broadcast channel))    -   TDM: time division multiplexing    -   TRP: transmission and reception point    -   TRS: tracking reference signal    -   Tx: transmission    -   UE: user equipment    -   ZP: zero power

Overall System

As more communication devices have required a higher capacity, a needfor an improved mobile broadband communication compared to the existingradio access technology (RAT) has emerged. In addition, massive MTC(Machine Type Communications) providing a variety of services anytimeand anywhere by connecting a plurality of devices and things is also oneof main issues which will be considered in a next-generationcommunication. Furthermore, a communication system design considering aservice/a terminal sensitive to reliability and latency is alsodiscussed. As such, introduction of a next-generation RAT consideringeMBB(enhanced mobile broadband communication), mMTC(massive MTC),URLLC(Ultra-Reliable and Low Latency Communication), etc. is discussedand, for convenience, a corresponding technology is referred to as NR inthe present disclosure. NR is an expression which represents an exampleof a 5G RAT.

A new RAT system including NR uses an OFDM transmission method or atransmission method similar to it. A new RAT system may follow OFDMparameters different from OFDM parameters of LTE. Alternatively, a newRAT system follows a numerology of the existing LTE/LTE-A as it is, butmay support a wider system bandwidth (e.g., 100 MHz). Alternatively, onecell may support a plurality of numerologies. In other words, terminalswhich operate in accordance with different numerologies may coexist inone cell.

A numerology corresponds to one subcarrier spacing in a frequencydomain. As a reference subcarrier spacing is scaled by an integer N, adifferent numerology may be defined.

FIG. 1 illustrates a structure of a wireless communication system towhich the present disclosure may be applied.

In reference to FIG. 1 , NG-RAN is configured with gNBs which provide acontrol plane (RRC) protocol end for a NG-RA(NG-Radio Access) user plane(i.e., a new AS(access stratum) sublayer/PDCP(Packet Data ConvergenceProtocol)/RLC(Radio Link Control)/MAC/PHY) and UE. The gNBs areinterconnected through a Xn interface. The gNB, in addition, isconnected to an NGC(New Generation Core) through an NG interface. Inmore detail, the gNB is connected to an AMF(Access and MobilityManagement Function) through an N2 interface, and is connected to aUPF(User Plane Function) through an N3 interface.

FIG. 2 illustrates a frame structure in a wireless communication systemto which the present disclosure may be applied.

A NR system may support a plurality of numerologies. Here, a numerologymay be defined by a subcarrier spacing and a cyclic prefix (CP)overhead. Here, a plurality of subcarrier spacings may be derived byscaling a basic (reference) subcarrier spacing by an integer N (or, μ).In addition, although it is assumed that a very low subcarrier spacingis not used in a very high carrier frequency, a used numerology may beselected independently from a frequency band. In addition, a variety offrame structures according to a plurality of numerologies may besupported in a NR system.

Hereinafter, an OFDM numerology and frame structure which may beconsidered in a NR system will be described. A plurality of OFDMnumerologies supported in a NR system may be defined as in the followingTable 1.

TABLE 1 μ Δf = 2^(μ) · 15 [kHz] CP 0 15 Normal 1 30 Normal 2 60 Normal,Extended 3 120 Normal 4 240 Normal

NR supports a plurality of numerologies (or subcarrier spacings (SCS))for supporting a variety of 5G services. For example, when a SCS is 15kHz, a wide area in traditional cellular bands is supported, and when aSCS is 30kHz/60 kHz, dense-urban, lower latency and a wider carrierbandwidth are supported, and when a SCS is 60 kHz or higher, a bandwidthwider than 24.25 GHz is supported to overcome a phase noise.

An NR frequency band is defined as a frequency range in two types (FR1,FR2). FR1, FR2 may be configured as in the following Table 2. Inaddition, FR2 may mean a millimeter wave (mmW).

TABLE 2 Frequency Range designation Corresponding frequency rangeSubcarrier Spacing FR1  410 MHz-7125 MHz  15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

Regarding a frame structure in an NR system, a size of a variety offields in a time domain is expresses as a multiple of a time unit ofT_(c)=1/(Δf_(max)·N_(f)). Here, Δf_(max) is 480·10³ Hz and N_(f) is4096. Downlink and uplink transmission is configured (organized) with aradio frame having a duration of T_(f)=1/(Δf_(max)N_(f)/100)·T_(c)=10ms. Here, a radio frame is configured with 10 subframes having aduration of T_(sf)=(Δf_(max)N_(f)/1000)·T_(c)=1 ms, respectively. Inthis case, there may be one set of frames for an uplink and one set offrames for a downlink. In addition, transmission in an uplink frame No.i from a terminal should start earlier byT_(TA)=(N_(TA)+N_(TA,offset))T_(c) than a corresponding downlink framein a corresponding terminal starts. For a subcarrier spacingconfiguration μ, slots are numbered in an increasing order of n_(s)^(μ)∈{0, . . . , N_(slot) ^(subframe,μ)−1} in a subframe and arenumbered in an increasing order of n_(s,f) ^(μ)∈{0, . . . , N_(slot)^(frame,μ)−1} in a radio frame. One slot is configured with N_(symb)^(slot) consecutive OFDM symbols and N_(symb) ^(slot) is determinedaccording to CP. A start of a slot n_(s) ^(μ) subframe is temporallyarranged with a start of an OFDM symbol n_(s) ^(μ)N_(symb) ^(slot) inthe same subframe. All terminals may not perform transmission andreception at the same time, which means that all OFDM symbols of adownlink slot or an uplink slot may not be used.

Table 3 represents the number of OFDM symbols per slot (N_(symb)^(slot)), the number of slots per radio frame (N_(slot) ^(frame,μ)) andthe number of slots per subframe (N_(slot) ^(subframe,μ)) in a normal CPand Table 4 represents the number of OFDM symbols per slot, the numberof slots per radio frame and the number of slots per subframe in anextended CP.

TABLE 3 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

TABLE 4 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)2 12 40 4

FIG. 2 is an example on μ=2 (SCS is 60 kHz), 1 subframe may include 4slots referring to Table 3. 1 subframe={1,2,4} slot shown in FIG. 2 isan example, the number of slots which may be included in 1 subframe isdefined as in Table 3 or Table 4. In addition, a mini-slot may include2, 4 or 7 symbols or more or less symbols.

Regarding a physical resource in a NR system, an antenna port, aresource grid, a resource element, a resource block, a carrier part,etc. may be considered. Hereinafter, the physical resources which may beconsidered in an NR system will be described in detail.

First, in relation to an antenna port, an antenna port is defined sothat a channel where a symbol in an antenna port is carried can beinferred from a channel where other symbol in the same antenna port iscarried. When a large-scale property of a channel where a symbol in oneantenna port is carried may be inferred from a channel where a symbol inother antenna port is carried, it may be said that 2 antenna ports arein a QC/QCL(quasi co-located or quasi co-location) relationship. In thiscase, the large-scale property includes at least one of delay spread,doppler spread, frequency shift, average received power, receivedtiming.

FIG. 3 illustrates a resource grid in a wireless communication system towhich the present disclosure may be applied.

In reference to FIG. 3 , it is illustratively described that a resourcegrid is configured with N_(RB) ^(μ)N_(sc) ^(RB) subcarriers in afrequency domain and one subframe is configured with 14·2^(μ) OFDMsymbols, but it is not limited thereto. In an NR system, a transmittedsignal is described by OFDM symbols of 2^(μ)N_(symb)(^(μ)) and one ormore resource grids configured with N_(RB) ^(μ)N_(sc) ^(RB) subcarriers.Here, N_(RB) ^(μ)≤N_(RB) ^(max,μ). The N_(RB) ^(max,μ) represents amaximum transmission bandwidth, which may be different between an uplinkand a downlink as well as between numerologies. In this case, oneresource grid may be configured per μ and antenna port p. Each elementof a resource grid for μ and an antenna port p is referred to as aresource element and is uniquely identified by an index pair (k,l′).Here, k=0, . . . , N_(RB) ^(μ)N_(sc) ^(RB)−1 is an index in a frequencydomain and l′=0, . . . , 2^(μ)N_(symb) ^((μ))−1 refers to a position ofa symbol in a subframe. When referring to a resource element in a slot,an index pair (k,l) is used. Here, l=0, . . . , N_(symb) ^(μ)−1. Aresource element (k,l′) for μ and an antenna port p corresponds to acomplex value, a_(k,l′) ^((p,μ)). When there is no risk of confusion orwhen a specific antenna port or numerology is not specified, indexes pand μ may be dropped, whereupon a complex value may be a_(k,l′) ^((p))or a_(k,l′). In addition, a resource block (RB) is defined as N_(sc)^(RB)=12 consecutive subcarriers in a frequency domain.

Point A plays a role as a common reference point of a resource blockgrid and is obtained as follows.

-   -   offsetToPointA for a primary cell (PCell) downlink represents a        frequency offset between point A and the lowest subcarrier of        the lowest resource block overlapped with a SS/PBCH block which        is used by a terminal for an initial cell selection. It is        expressed in resource block units assuming a 15 kHz subcarrier        spacing for FR1 and a 60 kHz subcarrier spacing for FR2.    -   absoluteFrequencyPointA represents a frequency-position of point        A expressed as in ARFCN (absolute radio-frequency channel        number).

Common resource blocks are numbered from 0 to the top in a frequencydomain for a subcarrier spacing configuration μ. The center ofsubcarrier 0 of common resource block 0 for a subcarrier spacingconfiguration μ is identical to ‘point A’. A relationship between acommon resource block number n_(CRB) ^(μ) and a resource element (k,l)for a subcarrier spacing configuration μ in a frequency domain is givenas in the following Equation 1.

$\begin{matrix}{n_{CRB}^{\mu} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

In Equation 1, k is defined relatively to point A so that k=0corresponds to a subcarrier centering in point A. Physical resourceblocks are numbered from 0 to N_(BWP,i) ^(size,μ)−1 in a bandwidth part(BWP) and i is a number of a BWP. A relationship between a physicalresource block n_(pRB) and a common resource block n_(CRB) in BWP i isgiven by the following Equation 2.

n _(CRB) ^(μ) =n _(PRB) ^(μ) +N _(BWP,i) ^(start,μ)  (2)

N_(BWP,i) ^(start,μ) is a common resource block that a BWP startsrelatively to common resource block 0.

FIG. 4 illustrates a physical resource block in a wireless communicationsystem to which the present disclosure may be applied. And, FIG. 5illustrates a slot structure in a wireless communication system to whichthe present disclosure may be applied.

In reference to FIG. 4 and FIG. 5 , a slot includes a plurality ofsymbols in a time domain. For example, for a normal CP, one slotincludes 7 symbols, but for an extended CP, one slot includes 6 symbols.

A carrier includes a plurality of subcarriers in a frequency domain. AnRB (Resource Block) is defined as a plurality of (e.g., 12) consecutivesubcarriers in a frequency domain. A BWP(Bandwidth Part) is defined as aplurality of consecutive (physical) resource blocks in a frequencydomain and may correspond to one numerology (e.g., an SCS, a CP length,etc.). A carrier may include a maximum N (e.g., 5) BWPs. A datacommunication may be performed through an activated BWP and only one BWPmay be activated for one terminal. In a resource grid, each element isreferred to as a resource element (RE) and one complex symbol may bemapped.

In an NR system, up to 400 MHz may be supported per component carrier(CC). If a terminal operating in such a wideband CC always operatesturning on a radio frequency (FR) chip for the whole CC, terminalbattery consumption may increase. Alternatively, when severalapplication cases operating in one wideband CC (e.g., eMBB, URLLC, Mmtc,V2X, etc.) are considered, a different numerology (e.g., a subcarrierspacing, etc.) may be supported per frequency band in a correspondingCC. Alternatively, each terminal may have a different capability for themaximum bandwidth. By considering it, a base station may indicate aterminal to operate only in a partial bandwidth, not in a full bandwidthof a wideband CC, and a corresponding partial bandwidth is defined as abandwidth part (BWP) for convenience. A BWP may be configured withconsecutive RBs on a frequency axis and may correspond to one numerology(e.g., a subcarrier spacing, a CP length, a slot/a mini-slot duration).

Meanwhile, a base station may configure a plurality of BWPs even in oneCC configured to a terminal. For example, a BWP occupying a relativelysmall frequency domain may be configured in a PDCCH monitoring slot, anda PDSCH indicated by a PDCCH may be scheduled in a greater BWP.Alternatively, when UEs are congested in a specific BWP, some terminalsmay be configured with other BWP for load balancing. Alternatively,considering frequency domain inter-cell interference cancellationbetween neighboring cells, etc., some middle spectrums of a fullbandwidth may be excluded and BWPs on both edges may be configured inthe same slot. In other words, a base station may configure at least oneDL/UL BWP to a terminal associated with a wideband CC. A base stationmay activate at least one DL/UL BWP of configured DL/UL BWP(s) at aspecific time (by L1 signaling or MAC CE(Control Element) or RRCsignaling, etc.). In addition, a base station may indicate switching toother configured DL/UL BWP (by L1 signaling or MAC CE or RRC signaling,etc.). Alternatively, based on a timer, when a timer value is expired,it may be switched to a determined DL/UL BWP. Here, an activated DL/ULBWP is defined as an active DL/UL BWP. But, a configuration on a DL/ULBWP may not be received when a terminal performs an initial accessprocedure or before a RRC connection is set up, so a DL/UL BWP which isassumed by a terminal under these situations is defined as an initialactive DL/UL BWP.

FIG. 6 illustrates physical channels used in a wireless communicationsystem to which the present disclosure may be applied and a generalsignal transmission and reception method using them.

In a wireless communication system, a terminal receives informationthrough a downlink from a base station and transmits information throughan uplink to a base station.

Information transmitted and received by a base station and a terminalincludes data and a variety of control information and a variety ofphysical channels exist according to a type/a usage of informationtransmitted and received by them.

When a terminal is turned on or newly enters a cell, it performs aninitial cell search including synchronization with a base station or thelike (S601). For the initial cell search, a terminal may synchronizewith a base station by receiving a primary synchronization signal (PSS)and a secondary synchronization signal (SSS) from a base station andobtain information such as a cell identifier (ID), etc. After that, aterminal may obtain broadcasting information in a cell by receiving aphysical broadcast channel (PBCH) from a base station. Meanwhile, aterminal may check out a downlink channel state by receiving a downlinkreference signal (DL RS) at an initial cell search stage.

A terminal which completed an initial cell search may obtain moredetailed system information by receiving a physical downlink controlchannel (PDCCH) and a physical downlink shared channel (PDSCH) accordingto information carried in the PDCCH (S602).

Meanwhile, when a terminal accesses to a base station for the first timeor does not have a radio resource for signal transmission, it mayperform a random access (RACH) procedure to a base station (S603 toS606). For the random access procedure, a terminal may transmit aspecific sequence as a preamble through a physical random access channel(PRACH) (S603 and S605) and may receive a response message for apreamble through a PDCCH and a corresponding PDSCH (S604 and S606). Acontention based RACH may additionally perform a contention resolutionprocedure.

A terminal which performed the above-described procedure subsequentlymay perform PDCCH/PDSCH reception (S607) and PUSCH(Physical UplinkShared Channel)/PUCCH(physical uplink control channel) transmission(S608) as a general uplink/downlink signal transmission procedure. Inparticular, a terminal receives downlink control information (DCI)through a PDCCH. Here, DCI includes control information such as resourceallocation information for a terminal and a format varies depending onits purpose of use.

Meanwhile, control information which is transmitted by a terminal to abase station through an uplink or is received by a terminal from a basestation includes a downlink/uplinkACK/NACK(Acknowledgement/Non-Acknowledgement) signal, a CQI(ChannelQuality Indicator), a PMI(Precoding Matrix Indicator), a RI(RankIndicator), etc. For a 3GPP LTE system, a terminal may transmit controlinformation of the above-described CQI/PMI/RI, etc. through a PUSCHand/or a PUCCH.

Table 5 represents an example of a DCI format in an NR system.

TABLE 5 DCI Format Use 0_0 Scheduling of a PUSCH in one cell 0_1Scheduling of one or multiple PUSCHs in one cell, or indication of cellgroup downlink feedback information to a UE 0_2 Scheduling of a PUSCH inone cell 1_0 Scheduling of a PDSCH in one DL cell 1_1 Scheduling of aPDSCH in one cell 1_2 Scheduling of a PDSCH in one cell

In reference to Table 5, DCI formats 0_0, 0_1 and 0_2 may includeresource information (e.g., UL/SUL(Supplementary UL), frequency resourceallocation, time resource allocation, frequency hopping, etc.),information related to a transport block(TB) (e.g., MCS(ModulationCoding and Scheme), a NDI(New Data Indicator), a RV(Redundancy Version),etc.), information related to a HARQ(Hybrid—Automatic Repeat andrequest) (e.g., a process number, a DAI(Downlink Assignment Index),PDSCH-HARQ feedback timing, etc.), information related to multipleantennas (e.g., DMRS sequence initialization information, an antennaport, a CSI request, etc.), power control information (e.g., PUSCH powercontrol, etc.) related to scheduling of a PUSCH and control informationincluded in each DCI format may be pre-defined.

DCI format 0_0is used for scheduling of a PUSCH in one cell. Informationincluded in DCI format 0_0is CRC (cyclic redundancy check) scrambled bya C-RNTI(Cell Radio Network Temporary Identifier) or aCS-RNTI(Configured Scheduling RNTI) or a MCS-C-RNTI(Modulation CodingScheme Cell RNTI) and transmitted.

DCI format 0_1 is used to indicate scheduling of one or more PUSCHs orconfigure grant (CG) downlink feedback information to a terminal in onecell. Information included in DCI format 0_1 is CRC scrambled by aC-RNTI or a CS-RNTI or a SP-CSI-RNTI(Semi-Persistent CSI RNTI) or aMCS-C-RNTI and transmitted.

DCI format 0_2 is used for scheduling of a PUSCH in one cell.Information included in DCI format 0_2 is CRC scrambled by a C-RNTI or aCS-RNTI or a SP-CSI-RNTI or a MCS-C-RNTI and transmitted.

Next, DCI formats 1_0, 1_1 and 1_2 may include resource information(e.g., frequency resource allocation, time resource allocation,VRB(virtual resource block)-PRB(physical resource block) mapping, etc.),information related to a transport block(TB)(e.g., MCS, NDI, RV, etc.),information related to a HARQ (e.g., a process number, DAI, PDSCH-HARQfeedback timing, etc.), information related to multiple antennas (e.g.,an antenna port, a TCI(transmission configuration indicator), aSRS(sounding reference signal) request, etc.), information related to aPUCCH (e.g., PUCCH power control, a PUCCH resource indicator, etc.)related to scheduling of a PDSCH and control information included ineach DCI format may be pre-defined.

DCI format 1_0is used for scheduling of a PDSCH in one DL cell.Information included in DCI format 1_0is CRC scrambled by a C-RNTI or aCS-RNTI or a MCS-C-RNTI and transmitted.

DCI format 1_1 is used for scheduling of a PDSCH in one cell.Information included in DCI format 1_1 is CRC scrambled by a C-RNTI or aCS-RNTI or a MCS-C-RNTI and transmitted.

DCI format 1_2 is used for scheduling of a PDSCH in one cell.Information included in DCI format 1_2 is CRC scrambled by a C-RNTI or aCS-RNTI or a MCS-C-RNTI and transmitted.

A Wireless Communication System Supporting a Non-Terrestrial Network(NTN)

NTN refers to a network or a segment of a network configured to use aradio resource (RF resource) in a satellite or unmanned aircraft system(UAS) platform. In order to secure wider coverage or to provide awireless communication service in a place where it is not easy toinstall a wireless communication base station, the use of the NTNservice is being considered.

Here, the NTN service refers to providing a wireless communicationservice to UEs by installing a base station on an artificialsatellite(e.g., geostationary-orbit, low-orbit, medium-orbit satellite,etc.), an airplane, an unmanned aerial vehicle, a drone, etc. ratherthan on the ground. In the following description, the NTN service mayinclude an NR NTN service and/or an LTE NTN service. A terrestrialnetwork (TN) service refers to providing a wireless communicationservice to UEs by installing a base station on the ground.

A frequency band considered for the NTN service may be a 2 GHz band(S-band: 2-4 GHz) in the frequency range 1 (FR1)(e.g., 410 MHz to 7.125GHz), and a downlink 20 GHz and uplink 30 GHz band (Ka-Band: 26.5˜40GHz)in the frequency range 2(FR2). Additionally, the NTN service may besupported in a frequency band between 7.125 GHz and 24.25 GHz or in afrequency band of 52.6 GHz or higher.

FIGS. 7A and 7B are diagrams for describing NTN supported by a wirelesscommunication system to which the present disclosure may be applied.

FIG. 7A illustrates an NTN scenario based on a transparent payload(transparent payload) and FIG. 7B illustrates an NTN scenario based on aregenerative payload (regenerative payload).

Here, the NTN scenario based on the transparent payload is a scenario inwhich an artificial satellite that has received a payload from aterrestrial base station transmits the corresponding payload to the UE,and the NTN scenario based on the regenerative payload refers to ascenario in which an artificial satellite is implemented as a basestation (gNB).

NTNs are typically characterized by the following elements:

-   -   one or more satellite-gateways for connecting NTN to public data        networks:

A geostationary earth orbiting (GEO) satellite is fed by one or moresatellite-gateways that are deployed in coverage targeted by thesatellite (e.g., regional or continental coverage). A UE in a cell maybe assumed to be served by only one satellite-gateway.

Non-GEO satellites may be successively served by one or moresatellite-gateways. At this time, the wireless communication systemguarantees service and feeder link continuity between the servingsatellite-gateways for a time period sufficient to proceed with mobilityanchoring and hand-over.

-   -   A feeder link or radio link between the satellite-gateway and        the satellite (or UAS platform)    -   Service link or radio link between the UE and the satellite (or        UAS platform)    -   A satellite (or UAS platform) capable of implementing either a        transparent or a regenerated (including on-board processing)        payload.

Satellite (or UAS platform) generated beams generally generate aplurality of beams in a service area bounded by the field of view of thesatellite (or UAS platform). The footprint of the beam is generallyelliptical. The view of the satellite (or UAS platform) is determined bythe onboard antenna diagram and the minimum elevation angle.

Transparent Payload: radio frequency filtering, frequency conversion andamplification. Accordingly, the waveform signal repeated by the payloadis un-changed.

Regenerative payload: radio frequency filtering, frequencytransformation and amplification as well as demodulation/decoding,switching and/or routing, coding/modulation. This is effectivelyequivalent to having all or part of the base station functions (e.g.gNB) on a satellite (or UAS platform).

-   -   Inter-satellite links (ISL) for satellite groups. This requires        a regenerative payload on the satellite. ISLs may operate at RF        frequencies or optical bands.    -   The UE is serviced by a satellite (or UAS platform) within the        target service area.

Table 6 illustrates the types of satellites (or UAS platforms).

TABLE 6 Typical beam Platform Altitude range Orbit footprint sizeLow-Earth Orbit 300-1500 km Circular around 100-1000 km (LEO) satellitethe earth Medium-Earth 7000-25000 km  100-1000 km Orbit (MEO) satelliteGeostationary  35 786 km notional station 200-3500 km Earth Orbit (GEO)keeping position satellite fixed in terms of UAS platform   8-50 kmelevation/azimuth   5-200 km (including HAPS) (20 km for with respect toa HAPS) given earth point High Elliptical 400-50000 km  Ellipticalaround 200-3500 km Orbit (HEO) the earth satellite

Typically, GEO satellites and UAS are used to provide continental,regional or local services. And, a constellation of low earth orbiting(LEO) and medium earth orbiting (MEO) is used to provide services inboth the northern and southern hemispheres. Alternatively, thecorresponding constellation may provide global coverage including thepolar region. In the future, appropriate orbital inclination, sufficientbeams generated and inter-satellite links may be required. In addition,a highly elliptical orbiting (HEO) satellite system may be considered.

Hereinafter, a wireless communication system in NTN including thefollowing six reference scenarios will be described.

-   -   Circular orbiting and notional station keeping platforms.    -   Highest RTD (Round Trip Delay) constraint    -   Highest Doppler constraint    -   A transparent and a regenerative payload    -   One ISL case and one without ISL case. Regenerative payload for        inter-satellite links

The six reference scenarios are considered in Tables 7 and 8.

TABLE 7 Transparent Regenerative satellite satellite GEO basednon-terrestrial access network Scenario A Scenario B LEO basednon-terrestrial access network: Scenario C1 Scenario D1 steerable beamsLEO based non-terrestrial access network: Scenario C2 Scenario D2 thebeams move with the satellite

TABLE 8 GEO based non-terrestrial LEO based access networknon-terrestrial (Scenario access network Scenarios A and B) (Scenario C& D) Orbit type notional station keeping circular orbiting positionfixed in terms around the earth of elevation/azimuth with respect to agiven earth point Altitude 35,786 km 600 km 1,200 km Spectrum (serviceIn FR1 (e.g., 2 GHz) link) IN FR2 (e.g., DL 20 GHz, UL 30 GHz) Maxchannel 30 MHz in FR1 bandwidth 1 GHz in FR2 capability (service link)Payload Scenario A: Scenario C: Transparent Transparent (including radio(including radio frequency function frequency function only) only)Scenario B: Scenario D: regenerative Regenerative (including all or partof (including all or part RAN functions) of RAN functions)Inter-Satellite link No Scenario C: No Scenario D: Yes/No (Both casesare possible.) Earth-fixed beams Yes Scenario C1: Yes (steerable beams),see note 1 Scenario C2: No (the beams move with the satellite) ScenarioD 1: Yes (steerable beams), see note 1 Scenario D 2: No (the beams movewith the satellite) Max beam foot 3500 km (Note 5) 1000 km print size(edge to edge) regardless of the elevation angle Min Elevation 10° forservice link and 10° for service link angle for both sat- 10° for feederlink and 10° for feeder link gateway and user equipment Max distance40,581 km 1,932 km (600 km between satellite altitude) and user 3,131 km(1,200 km equipment at min altitude) elevation angle Max Round TripScenario A: 541.46 ms Scenario C: Delay (propagation (service and feeder(transparent payload: delay only) links) service and feeder Scenario B:270.73 ms links) (service link only) 25.77 ms (600 km) 41.77 ms (1200km) Scenario D: (regenerative payload: service link only) 12.89 ms (600km) 20.89 ms (1200 km) Max differential 10.3 ms 3.12 ms and 3.18 msdelay within a cell for respectively 600 (Note 6) km and 1200 km MaxDoppler shift 0.93 ppm 24 ppm (600 km) (earth fixed user 21 ppm( 1200km) equipment) Max Doppler shift 0.000 045 ppm/s 0.27 ppm/s (600 km)variation (earth 0.13 ppm/s(1200 km) fixed user equipment) Userequipment 1200 km/h (e.g. 500 km/h (e.g. high motion on the aircraft)speed train) earth Possibly 1200 km/h (e.g. aircraft) User equipmentOmnidirectional antenna (linear polarisation), antenna types assuming 0dBi Directive antenna (up to 60 cm equivalent aperture diameter incircular polarisation) User equipment Tx Omnidirectional antenna: UEpower class 3 power with up to 200 mW Directive antenna: up to 20 W Userequipment Omnidirectional antenna: 7 dB Noise figure Directive antenna:1.2 dB Service link 3GPP defined New Radio Feeder link 3 GPP or non-3GPP3GPP or non-3GPP defined Radio interface defined Radio interface NOTE 1:Each satellite may have the capability to steer beams towards fixedpoints on earth using beamforming techniques. This is applicable for aperiod of time corresponding to the visibility time of the satellite.NOTE 2: Max delay variation within a beam (earth fixed user equipment)is calculated based on Min Elevation angle for both gateway and userequipment. NOTE 3: Max differential delay within a beam is calculatedbased on Max beam foot print diameter at nadir NOTE 4: Speed of lightused for delay calculation is 299792458 m/s. NOTE 5: The Maximum beamfoot print size for GEO is based on current state of the art GEO HighThroughput systems, assuming either spot beams at the edge of coverage(low elevation). NOTE 6: The maximum differential delay at the celllevel is calculated by considering the delay at the beam level for thelargest beam size. When the beam size is small or medium, the cell maycontain more than one beam. However, the cumulative differential delayof all beams in the cell does not exceed the maximum differential delayat the cell level in Table 8.

NOTE 1: Each satellite may have the capability to steer beams towardsfixed points on earth using beamforming techniques. This is applicablefor a period of time corresponding to the visibility time of thesatellite.

NOTE 2: Max delay variation within a beam (earth fixed user equipment)is calculated based on Min Elevation angle for both gateway and userequipment.

NOTE 3: Max differential delay within a beam is calculated based on Maxbeam foot print diameter at nadir.

NOTE 4: Speed of light used for delay calculation is 99792458 m/s.

NOTE 5: The Maximum beam foot print size for GEO is based on currentstate of the art GEO High Throughput systems, assuming either spot beamsat the edge of coverage (low elevation).

NOTE 6: The maximum differential delay at the cell level is calculatedby considering the delay at the beam level for the largest beam size.When the beam size is small or medium, the cell may contain more thanone beam. However, the cumulative differential delay of all beams in thecell does not exceed the maximum differential delay at the cell level inTable 8.

NTN-related descriptions in this disclosure may be applied to NTN GEOscenarios and all NGSO (non-geostationary orbit) scenarios with circularorbits with an altitude of 600 km or more.

In addition, the above-described contents (NR frame structure, NTN,etc.) may be applied in combination with methods to be described later,and may be supplemented to clarify the technical characteristics of themethod described in the present disclosure.

A Method for Configuring Timing Advance (TA) Value in NTN

In the TN, since the UE moves within a cell, even if the distancebetween the base station and the UE changes, the PRACH preambletransmitted by the UE may be transmitted to the base station within thetime duration of a specific RACH occasion (RO).

In addition, the TA value for the UE to transmit an uplinksignal/channel may include an initial TA value and a TA offset value.Here, the initial TA value and the TA offset value may be indicated bythe base station as a TA value expressible in the cell coverage range ofthe base station.

As another example, when the base station indicates a PDCCH orderthrough DCI, the UE may transmit a PRACH preamble to the base station.The UE may transmit an uplink signal/channel to the base station byusing the TA value (i.e., the initial TA value) indicated through theresponse message (random access response, RAR) to the preamble receivedfrom the base station.

In NTN, the distance between the satellite and the UE is changed due tothe movement of the satellite regardless of the movement of the UE. Toovercome this, the UE may determine the location of the terminal througha global navigation satellite system (GNSS), and calculate a UE-specificTA, which is a round trip delay (RTD) between the UE and the satellite,based on orbit information of the satellite instructed by the basestation.

Here, the UE-specific TA may be configured such that, when the PRACHpreamble is transmitted from the RO selected by the UE, the satellite(or the base station (gNB)) may receive the PRACH preamble within thetime period of the RO.

And, when only the UE-specific TA is applied when the PRACH preamble istransmitted from the RO selected by the UE, the PRACH preamble may betransmitted to the satellite (or gNB) with a delay from the referencetime of the RO. In this case, the initial TA value indicated by the RARreceived from the base station may indicate the delayed value.

Additionally, a common TA may mean an RTD between a gNB (or a referencepoint) on the ground and a satellite. Here, the reference point may meana place where downlink and uplink frame boundaries coincide. Inaddition, the common TA may be defined as indicated by the base stationto the UE. If the reference point is in the satellite, the common TA maynot be indicated, and if the reference point is in the gNB on theground, the common TA may be used to compensate for the RTD between thegNB and the satellite.

Additionally, in NTN, the TA value before transmission of message(message, Msg) 1 (e.g., PRACH preamble)/Msg A (e.g., PRACH preamble andPUSCH) may be configured to UE-specific TA and common TA (if provided).Here, the UE-specific TA may be an RTD between the UE and the satellitecalculated by the UE itself as described above.

As an embodiment of the present disclosure, FIGS. 8A and 8B illustrate amethod of calculating a TA value in a wireless communication systemsupporting NTN.

FIG. 8A illustrates a regenerative payload based NTN scenario. Thecommon TA (Tcom) (common to all UEs) may be calculated as 2D0(distancebetween the satellite and the reference signal)/c, and the UE-specificdifferential TA (TUEx) for the x-th UE (UEx) may be calculated as2(D1x−D0)/c. The total TA (Tfull) may be calculated as ‘Tcom+TUEx’.Here, D1x may mean a distance between the satellite and UEx and c mayrepresent the speed of light.

FIG. 8B illustrates a transparent payload based NTN scenario. The commonTA (Tcom) (common to all UEs) may be calculated as 2(D01+D02)/c, and theUE-specific differential TA (TUEx) for the x-th UE (UEx) may becalculated as 2(D1x−D0)/c. The total TA (Tfull) may be calculated as‘Tcom+TUEx’. Here, D01 may mean a distance between a satellite and areference point, and D02 may mean a distance between a satellite and abase station located on the ground.

Hereinafter, a method for the UE to obtain UE-specific TA based onsatellite ephemeris information within a validity duration will bedescribed with reference to FIG. 9 .

FIG. 9 is a flowchart illustrating a method of performing communicationof a UE in a wireless communication system to which the presentdisclosure may be applied.

In describing the present disclosure, a validity duration (or a validitywindow) may mean a time duration between a time when a validity timerstarts and a time when a validity timer expires. In addition, thewireless communication system may refer to a non-terrestrial network(NTN) system, but is not limited thereto, and may refer to various typesof communication systems such as a terrestrial network (TN) system.

The UE may receive first satellite ephemeris information related to thefirst satellite and information related to the first validity durationcorresponding to the first satellite from the base station (S910).

Here, the first satellite ephemeris information related to the firstsatellite and the information related to the first validity duration maybe received from the base station through one signaling(e.g., higherlayer signaling), but are not limited thereto, and may be receivedthrough separate signaling. In addition, the first satellite ephemerisinformation related to the first satellite and the information relatedto the first validity duration may be received together from the basestation, but are not limited thereto and may be separately received fromthe base station.

In addition, the information related to the first validity duration mayinclude at least one of a start/expiration time point of the firstvalidity duration and a size of the first validity duration. As anotherexample, the information related to the first validity duration mayinclude information on the first validity timer having the firstvalidity duration.

The UE may obtain the first TA (or a first UE-specific TA) for the firstsatellite based on the first satellite ephemeris information beforerestarting, expiring, or stopping after the first validity timer startsbased on the first validity duration.

Specifically, referring to FIG. 11A, the first (satellite) ephemerisinformation may be valid within the first validity duration configuredby the base station (i.e., after the first validity duration starts andbefore it ends). That is, the UE may obtain the first TA based on thefirst (satellite) ephemeris information within the first validityduration. And, when the first validity duration ends (i.e., when itexpires), the first (satellite) ephemeris information may no longer bevalid for TA acquisition of the UE.

And, the satellite ephemeris information may be based on at least one ofa first ephemeris format or a second ephemeris format.

Here, the first ephemeris format may be based on at least one of aposition (or a position state vector) or a velocity (or a velocity statevector) of the satellite. And, the second ephemeris format may be basedon one or more orbital elements. The one or more orbital elements mayinclude, but are not limited to, at least one of a semi-major axis, aneccentricity, an argument of periapsis, a longitude of ascending node,an orbital inclination, or a mean anomaly.

The UE may restart the first validity timer based on receiving thesecond satellite ephemeris information related to the first satellitefrom the base station while the first validity timer having the firstvalidity duration is running (or before the first validity timer startsand expires) (S920).

That is, the UE may restart the first validity timer having the firstvalidity duration configured at the epoch time of assistance information(i.e., serving satellite ephemeris information).

Here, the size of the second validity duration of the restarted firstvalidity timer may be the same as the size of the first validityduration previously configured by the base station, but is not limitedthereto and may be different from each other.

The UE may obtain the second TA for the first satellite based on thesecond satellite ephemeris information before the first validity timerexpires or stops after restarting based on the second validity duration.Here, the first TA and the second TA may mean a UE-specific TA relatedto the first satellite.

Specifically, referring to FIG. 11B, if the second (satellite) ephemerisinformation is received from the base station before the first validitytimer expires or stops after starting based on the first validityduration, the UE may restart the first validity timer. And, after thefirst validity timer restarts based on the second validity duration, theUE may obtain a TA based on the second (satellite) ephemerisinformation.

FIG. 11B illustrates a case in which the first validity timer isrestarted when the second (satellite) ephemeris information is received,but is not limited thereto. The first validity timer may be restarted ata specific time between the time when the second (satellite) ephemerisinformation is received and the time when the existing first validityduration ends, and the restart time of the first validity timer may bepredefined.

In another embodiment, based on not receiving the second satelliteephemeris information within the first validity duration and based onthe expiration of the first validity timer, the first satelliteephemeris information may no longer be valid. Accordingly, the UE maynot perform the process of obtaining the TA for the first satellitebased on the first satellite ephemeris information.

In an embodiment of the present disclosure, the UE may receiveinformation related to the third validity duration corresponding to thesecond satellite from the base station. Here, the first satellite may bea serving satellite, and the second satellite may be a non-servingsatellite (or a neighbor satellite).

A serving satellite may be expressed as a satellite for a serving cell,and a non-serving satellite (or a neighboring satellite) may beexpressed as a satellite for a non-serving cell (or a satellite for aneighboring cell).

Here, the satellite ephemeris information and information related to thevalidity duration may be included in higher layer signaling (e.g., RRCsignaling, MAC-CE, etc.) and received from the base station.

In addition, the information related to the third validity duration mayinclude at least one of a start/expiration time point of the thirdvalidity duration and a size of the third validity duration. As anotherexample, the information related to the third validity duration mayinclude information on the second validity timer having the thirdvalidity duration.

In addition, the first validity timer corresponding to the firstsatellite and the second validity timer corresponding to the secondsatellite may operate independently. In addition, the validity durationof each of the first validity timer and the second validity timer mayalso be configured independently.

For example, the validity duration corresponding to the first satellite(e.g., the first and the second validity duration, etc.) and thevalidity duration corresponding to the second satellite(e.g., the thirdand the fourth validity duration, etc.) may be independently configured.

And, the first validity timer corresponding to the first satelliteoperates based on the validity duration for the satellite ephemerisinformation related to the first satellite, and the second validitytimer corresponding to the second satellite may operate based on thevalidity duration for satellite ephemeris information related to thesecond satellite.

Based on the third satellite ephemeris information related to the secondsatellite being received from the base station, the UE may acquire thethird TA for the second satellite based on the third satellite ephemerisinformation before restarting, expiring, or stopping after the secondvalidity timer having the third validity duration starts.

Based on the fourth satellite ephemeris information related to thesecond satellite being received from the base station while the secondvalidity timer is in operation, the second validity timer may berestarted by the UE.

That is, the UE may restart the second validity timer having the thirdvalidity duration configured at the epoch time of assistance information(i.e., satellite ephemeris information).

In addition, the UE may obtain the fourth TA based on the fourthsatellite ephemeris information before the second validity timer expiresor stops after restarting based on the fourth validity duration. Here,the third TA and the fourth TA may refer to UE-specific TAs related tothe second satellite.

In this case, the sizes of the third validity duration and the fourthvalidity duration may be the same, but are not limited thereto and maybe different from each other.

Hereinafter, a method in which a base station transmits informationrelated to a validity duration corresponding to a satellite to a UE willbe described with reference to FIG. 10 .

FIG. 10 is a flowchart illustrating a communication method of a basestation according to an embodiment of the present disclosure.

The base station may transmit first satellite ephemeris informationrelated to the first satellite and information related to the firstvalidity duration corresponding to the first satellite to the UE(S1010). Since the description related to the first satellite ephemerisinformation and the information related to the first validity durationhas been described with reference to FIG. 9 , a redundant descriptionwill be omitted.

After the first validity timer configured by the base station is startedbased on the first validity duration and then restarted, expired, orstopped, the UE may obtain the first TA for the first satellite based onthe first satellite ephemeris information.

The base station may transmit second satellite ephemeris informationrelated to the first satellite to the UE while the first validity timerhaving the first validity duration is operating (S1020).

After the first validity timer is started, the UE receiving the secondsatellite ephemeris information may restart the first validity timer. Inthis case, the size of the second validity duration of the restartedfirst validity timer may be the same as the size of the first validityduration previously configured by the base station.

In addition, the UE may obtain the second TA for the first satellitebased on the second satellite ephemeris information before the firstvalidity timer expires or stops after restarting based on the secondvalidity duration.

Hereinafter, a specific embodiment of the present disclosure related toan operation of acquiring a UE-specific TA based on satellite ephemerisinformation will be described.

The UE needs to know the satellite ephemeris (or/and, orbit) in order tocalculate the UE-specific TA. Accordingly, the base station mayconfigure/indicate the satellite ephemeris to the UE, or the UE may beconfigured to know the satellite ephemeris in advance (via USIM, etc.).In this case, the format of the satellite ephemeris may be implementedwith the following two options.

-   -   Option 1: satellite ephemeris format based on satellite position        and velocity state vectors (e.g., position and velocity vectors        (x, y, z) in a reference time epoch, vx, yy, yz))    -   Option 2: satellite ephemeris format based on orbit element        (e.g., orbit element (a, e, ω, Ω, i, MO))

The orbit state vector method, which is an example of the option 1, is amethod of expressing a satellite ephemeris using six elements (aposition vector and a velocity vector for each of the three directionsof x, y, and z). In the above method, the orbit of the satellite may beaccurately estimated only when the six elements are provided for eachepoch (reference) time.

As shown in FIG. 12 , the Kepler orbit elements method, which is anexample of option 2, is a method of expressing satellite orbits usingthe following six elements.

-   -   semi-major axis (half of the major axis of a satellite's orbit,        which is an ellipse) “a” [m]    -   eccentricity “e” (in an elliptical satellite orbit, 0<e<1)    -   argument of periapsis (it refers to the angle from the orbital        proximal point which is the point closest to the centroid when        the object orbits to the ascending node, and determines the        direction of the ellipse on the orbital plane.) “ω” [rad]    -   longitude of ascending node (the angle measured from the        reference point (e.g., the reference point in the solar system        is the vernal equinox) to the ascending node (i.e., the point at        which the orbit passes from below the reference plane upwards)        in a counterclockwise direction) “Ω” [rad]    -   (orbital) inclination (it refers to the degree of inclination of        the ellipse with respect to the reference plane, and is measured        as the angle between the raceway and the reference plane at the        ascending point.) “i” [rad]    -   mean anomaly(it refers to an angle that changes continuously        with time, which is mathematically convenient, but does not        coincide with the geometric angle.) “M0”=M(t0)[rad] at epoch t0        [JD]

Here, the mean anomaly may also be expressed as a true anomaly (“v”).The true anomaly value represents the angle between the orbitalperiapsis and the orbiting object at any point in time, so it coincideswith the geometrical angle. Accordingly, although the true anomaly isdisplayed in FIG. 12 , the mean anomaly is not displayed.

In the Kepler orbital element method described above, the first fiveelements (e.g., semi-major axis (half the length of the major axis),eccentricity, argument of periapsis, longitude of ascending node,orbital inclination) are not values that change with time, assuming thatthere is no severe interference. Accordingly, the mean anomaly (or trueanomaly) indicating the actual position of the satellite is a value tobe provided for each epoch (reference) time.

In the present disclosure, a method for signaling and updating theformats indicating the two ephemeris information from the base stationwill be described.

A method for Configuring Validity of Satellite Ephemeris Information

When the base station indicates all (or part of) satellite ephemerisinformation to the UE through a broadcast channel (e.g., SIB, RRCsignaling, etc.), the UE needs to determine how long the correspondingsatellite ephemeris information is valid. Accordingly, a validity window(or a validity timer) indicating the validity of the satellite ephemerisinformation may be configured.

Specifically, the base station may indicate/configure a duration inwhich the UE may use the satellite ephemeris informationindicated/configured for calculation of the UE-specific TA as anvalidity window. For example, the size (or duration) and/or applicationtime of the validity window may be signaled when the base stationbroadcasts satellite ephemeris information.

That is, when the validity window configured by the base station ends,the UE may configure to determine that the corresponding satelliteephemeris information is no longer valid. Therefore, in order for the UEto maintain valid satellite ephemeris information, the base stationneeds to update the satellite ephemeris information within thepreviously defined validity window.

When there is newly instructed/configured satellite ephemerisinformation, the UE may calculate a UE-specific TA by using thecorresponding information, and may newly configure an validity window ofthe satellite ephemeris information. For example, the UE may initializethe starting point of the validity window, and the duration (or size) ofthe validity window may be configured to be the same as the previouslyindicated/configured period (or size).

And, when the base station is configured/defined to periodicallybroadcast all (or part of) satellite ephemeris information, the UE mayexpect the base station to update the satellite ephemeris information inthe next period. Accordingly, at this time, the base station does notneed to define a separate validity window, and the UE may determine thatthe immediately preceding satellite ephemeris information is alwaysvalid until the satellite ephemeris information is updated from the basestation. And, since the UE completely trusts the information sent by thebase station and performs various operations, the base station needs toupdate the satellite ephemeris information accurately and at anappropriate time.

In an embodiment of the present disclosure, when a plurality ofdifferent satellite ephemeris information formats are used, the basestation may configure an independent validity timer (or validity window)for each format. Depending on the different satellite ephemerisinformation formats, the propagator model used may vary. Since theaccuracy of the satellite ephemeris information is different for eachsatellite ephemeris information format, the time for maintaining thevalidity of the ephemeris information for each satellite ephemerisinformation format may be different. Therefore, it may be necessary forthe base station to independently configure/indicate a validity windowfor each satellite ephemeris information format for efficient networkoperation.

For example, it may be considered that the validity timer A operates forthe satellite ephemeris information format X and the validity timer Boperates for the satellite ephemeris information format Y. The UE maydetermine the validity of each satellite ephemeris information accordingto whether each validity timer expires.

If all of the plurality of satellite ephemeris information formats arevalid, the base station may explicitly indicate which satelliteephemeris information the UE uses to calculate the UE-specific TA, whichmay be defined in advance. Alternatively, a method of preferentiallyusing satellite ephemeris information that expires first according tothe remaining time of the validity timer may be considered.Alternatively, a method of preferentially using the most recentlyindicated satellite ephemeris information format in time may also beconsidered.

If a single validity timer is used even though a plurality of differentsatellite ephemeris information formats are used, the following UEoperation may be required.

For example, in a situation where there is previously provided satelliteephemeris information format X and the validity timer A has not expired,considering the case where the base station provides the new satelliteephemeris information format Y, the UE may be configured to initializethe existing validity timer A value (i.e., to start a new validitywindow). Subsequently, the UE may determine that the previously providedsatellite ephemeris information format X is no longer valid.

That is, from the time the new satellite ephemeris information format Yis transmitted, the UE may configure/determine that only the satelliteephemeris information format Y is valid information until the validitytimer A expires.

In addition, the base station may independently configure/define theinitial value (or the duration of the validity window) of the validitytimer in advance according to each satellite ephemeris informationformat. As another example, the base station may directlyindicate/configure the initial value of the validity timer to the UEthrough signaling such as SIB/MAC-CE/RRC or by including it in a channelthrough which satellite ephemeris information is transmitted.

In an embodiment of the present disclosure, in order to check whethernew satellite ephemeris information is provided from the base stationwithin a validity duration for satellite ephemeris information, the UEmay be configured to monitor a downlink (DL) signal/channel (e.g., SIB,MAC-CE, RRC signaling, PDCCH) that provides satellite ephemerisinformation.

In this case, when new satellite ephemeris information is provided, theUE may determine that the existing satellite ephemeris information is nolonger valid and calculate a UE-specific TA using the new satelliteephemeris information. In addition, when new satellite ephemerisinformation is provided, it may be configured that a validity durationis newly started (re-start). In this case, the base station needs todeliver new satellite ephemeris information before the validity durationends/expires.

If new satellite ephemeris information is not provided from the basestation until the validity duration ends/expires (or if the UE does notreceive a DL signal/channel for delivering satellite ephemerisinformation), the UE determines that the existing satellite ephemerisinformation is no longer valid and may be configured/indicated to updatethe UE-specific TA value and/or stop the UE-specific TA (or fullreporting).

And, the UE may be configured to monitor until new satellite ephemerisinformation is provided through a specific DL signal/channel (e.g., SIB,MAC-CE, RRC signaling, PDCCH, etc.). At this time, the UE is configured(BRF or RLF declaration) to enter into the idle (idle)/inactive(inactive) mode in the connected mode (connected mode), or the UE may beconfigured to request an update request for satellite ephemerisinformation to the base station.

When new satellite ephemeris information is provided from the basestation after the validity duration ends/expires, the UE may beconfigured to update the UE-specific TA and/or report the UE-specific TA(or the entire TA) based on this value. If it enters the idle/inactivemode, the UE may be configured to re-enter the connected mode byperforming an initial access procedure once more. And, when newsatellite ephemeris information is provided from the base station andthe UE confirms it, the validity duration may be configured to startanew.

Additionally, even if the ephemeris information of the serving (or,non-serving) satellite is updated and indicated from the base stationthrough the DL signal/channel (e.g., SIB, MAC-CE, RRC signaling, PDCCH,etc.) before the validity duration ends/expires, the time point at whichthe UE updates the corresponding satellite ephemeris information may beconfigured as a specific time point between the time point when the DLsignal/channel is received and the time point at which the existingvalidity duration ends. In addition, the UE may be configured to(re)start the validity timer at the corresponding point in time toupdate the satellite ephemeris information.

In this case, the specific time may be defined in advance. For example,the specific time point may be defined as a time point preceding (orpassing) a specific offset from a time point of ending a validityduration or a time point passing (or preceding) a specific offset from atime point of receiving a DL signal/channel. Alternatively, the specifictime may be indicated by the base station.

Additionally, regardless of the time when the UE actually updates theserving (or non-serving (or, upcoming)) satellite orbit, the UE may beconfigured to (re)start the validity duration at the time of receivingthe DL signal/channel carrying the satellite ephemeris information(e.g., immediately after the last DL slot or after a specific processingtime has elapsed). Alternatively, as in the previous method, it may beconfigured that the validity duration (re)starts according to apredefined rule or at a specific time indicated by the base station.

In an embodiment of the present disclosure, when the serving satelliteis changed during the NTN service, the base station may provide the UEwith satellite ephemeris information for each of the serving satelliteand the non-serving satellite (or, an upcoming satellite).Characteristically, satellite ephemeris information may be provided tothe UE through different DL signals/channels depending on whether thesatellite is serving or non-serving. For example, the ephemerisinformation of the serving satellite may be transmitted through SIB, andthe ephemeris information of the non-serving satellite may be configuredto be transmitted through RRC signaling, MAC-CE, GC (groupcommon)-PDCCH, etc.

Alternatively, when ephemeris information of satellites usable inconnection with a specific gNB is transmitted through a specific DLsignal/channel, different IDs may be assigned to each satellite. IDsthat can be distinguished for each satellite may be configured to beadditionally indicated through a DL signal/channel through whichsatellite ephemeris information is transmitted.

That is, the UE may receive the satellite ID together when the satelliteephemeris information is transmitted from the base station. Accordingly,since the satellite ID is always transmitted from the base stationtogether with the satellite ephemeris information whether it is aserving satellite or a non-serving satellite, the UE may classify thesatellite ephemeris information for each satellite ID and use thedivided satellite ephemeris information when calculating/reporting theUE-specific TA for each satellite.

Characteristically, in the case of a moving cell (i.e., a system inwhich a cell moves according to a movement of a satellite), a method oftying a cell ID and a satellite ID may be considered.

Hereinafter, when the serving satellite is changed, a method ofconfiguring a validity duration will be described.

In the first method, an independent validity duration for each of one ora plurality of non-serving satellites (or one for satellites) may beconfigured separately from the validity duration for the servingsatellite. At this time, when the base station provides ephemerisinformation for the non-serving satellite to the UE and the UE receivesit, the validity duration for the non-serving satellite may be(re)started. The UE may be configured to determine that thecorresponding satellite ephemeris information is valid during the(re)started validity duration, and to calculate/report the UE-specificTA (based on the corresponding satellite ephemeris information).

In the second method, it may be configured to use one validity durationfor various satellite ephemeris information that can be used inconnection with a specific base station. In this case, when the basestation provides ephemeris information for the non-serving satellite tothe UE and the UE receives it, the validity duration may be configuredto be (re)started. During the (re)started validity duration, the UEdetermines that the ephemeris information for the existing servingsatellite is also valid as well as the ephemeris information for thenon-serving satellite, and calculates/reports the UE-specific TA basedon each ephemeris information.

In describing the present disclosure, the validity duration may besubstituted or used interchangeably with the validity window and/orvalidity timer.

A Method of Updating TA Depending on Whether or not Satellite EphemerisInformation is Updated

When the base station updates and indicates the UE all (or part of)satellite ephemeris information through a broadcast channel (e.g., SIB,RRC signaling, etc.), the UE-specific TA value calculated by the UEusing the updated satellite ephemeris information needs to be updated.

Hereinafter, a method for the UE to update the UE-specific TA valuebased on the updated satellite ephemeris information will be described.

As a first method, the moment the base station updates all (or part) ofthe satellite ephemeris information, the UE may be instructed/configuredto update the UE-specific TA. In this case, since the UE-specific TAvalue can be changed instantaneously as ephemeris information ischanged, there is an advantage in that the UE-specific TA value may bemore accurately obtained.

However, when the above-described first method is applied, the UE needsto update the UE-specific TA value even if the ephemeris informationthat is not significantly different from the existing ephemerisinformation is updated. Accordingly, the newly calculated UE-specific TAvalue may not be significantly different from the previously calculatedUE-specific TA value.

As a second method, when the difference (or error) between the orbit (orephemeris) estimated by the UE using the existing ephemeris informationand the updated ephemeris information is greater than or equal to thethreshold (e.g., when the absolute positions of the satellites along thetwo orbits differ by more than X m at a specific point in time), the UEmay be configured to update the UE-specific TA.

When the difference between the updated ephemeris information and theexisting ephemeris information is equal to or greater than a threshold,the difference in the UE-specific TA value may be significant.Accordingly, the UE may be configured to update the UE-specific TA valueonly when a specific condition (e.g., a difference between the updatedephemeris information and the existing ephemeris information is equal toor greater than a threshold) is satisfied.

Additionally, when the UE is in the idle/inactive mode, the base stationmay be configured to update all (or part of) satellite ephemerisinformation to the UE using a broadcast channel (e.g., SIB, etc.). And,for the UE that has entered the connected mode, the base station may beconfigured to update all (or part of) satellite ephemeris informationusing a broadcast channel (e.g., SIB, etc.) or/and UE-specific RRCsignaling. And, for the UE that has entered the connected mode, the basestation may be configured to update all (or part of) satellite ephemerisinformation through information such as group common (GC) DCI (i.e.,GC-PDCCH) or MAC-CE.

In an embodiment of the present disclosure, when all of the plurality ofsatellite ephemeris information formats are supported, the base stationmay select one of the plurality of formats and provide it to the UE inthe idle/inactive mode. In addition, the base station may provideanother satellite ephemeris information format together with thesatellite ephemeris information format (i.e. the selected satelliteephemeris information format already provided) to the UE entering theconnected mode through UE-specific RRC signaling (or GC-PDCCH orMAC-CE).

At this time, the UE receiving the two satellite ephemeris informationformats may be configured to use the most recently provided satelliteephemeris information or may be configured to use the first indicatedsatellite ephemeris information format (in terms of time) among thesatellite ephemeris information formats in which the validity timer hasnot expired.

Operation of the UE When a Plurality of Satellite Ephemeris InformationFormats are Used in the Improved NTN System

Hereinafter, an operation of a UE that may be performed when a pluralityof (e.g., two) formats capable of expressing satellite ephemerisinformation are used in the improved NTN system will be described.

In an embodiment of the present disclosure, a format representing aspecific satellite ephemeris may be configured/indicated as a defaultformat. That is, since the base station indicates/configures only adefault format among formats representing a plurality of satelliteorbits, signaling overhead may be reduced.

For example, a format (e.g., Kepler orbital elements (a, e, ω, Ω, i,M0)) representing a satellite ephemeris based on orbit element(s) may beconfigured/defined as a default format. Since some of the orbit elementsfor expressing the satellite ephemeris are values that do not changewith time, the signaling overhead of the base station may be reducedwhen the above format is used.

As another example, a format for displaying a satellite ephemeris basedon an orbit state vector (e.g., a position vector and a velocity vector(x, y, z, vx, vy, vz)) may be configured/indicated as a default format.Since the format may be directly used for various services such as NTNand HAPS/ATG, there may be an advantage in terms of versatility.

In addition, formats other than a default format among formatsrepresenting a plurality of satellite orbits may be configured/indicatedas an optional format.

Additionally, the default format may be configured/indicated throughSIB1, universal subscriber identity module (USIM), etc., and theremaining optional formats may be configured/indicated by other SIB ordedicated RRC signaling or MAC-CE.

As another embodiment of the present disclosure, the base station mayconfigure/indicate the UE to use an appropriate format among formatsrepresenting a plurality of satellite ephemeris according to thecapability of the UE.

For example, the base station may configure to use a format fordisplaying satellite ephemeris based on an orbit state vector for a UEsupporting HAPS/ATG. The base station may be configured to use a formatfor displaying satellite orbits based on orbit elements for UEs that donot support HAPS/ATG.

According to the above-described embodiment, the base station mayconfigure the UE to use an appropriate format according to thecapability of the UE. However, the base station needs to transmit all ofthe plurality of formats.

In another embodiment of the present disclosure, a base station or a UEmay configure/indicate a priority according to a satellite ephemerisinformation format.

For example, (according to the capability or service environment of theUE) the UE configures a priority in the satellite ephemeris informationformat and may be configured to use the highest priority format amongthe satellite ephemeris information formats indicated/configured (by thebase station).

As another example, the base station configures a priority for thesatellite ephemeris information format and informs the UE of it, and theUE may be configured to use the high priority format accordingly.

As another embodiment of the present disclosure, a method of combining aplurality of satellite ephemeris information may be configured/indicatedfor the UE.

For example, the base station configures/indicates the ephemerisinformation format based on the orbit element to the UE once in a longperiod, and the base station may be configured to configure/indicate theephemeris information format based on the orbit state vector to the UEin a short period.

The UE may more accurately estimate the satellite ephemeris (or orbit)by combining the plurality of satellite ephemeris information.

For example, the UE may predict the entire ephemeris and the currentsatellite position using ephemeris information based on orbit elements,and may check the difference (or error) by comparing the predictedresult and the ephemeris information based on the orbit state vector.

As another example, the UE may be configured to use the average orintermediate value of the positions of the satellites obtained accordingto satellite ephemeris information based on two methods (i.e., a methodbased on an orbit element and an orbit state vector).

As another embodiment of the present disclosure, it may be defined asdifferently configuring a TA margin and/or a K_offset margin for eachformat representing a specific satellite ephemeris (or orbit). Accuracyfor estimating a satellite position may be different when calculating aUE-specific TA value according to a format representing a satelliteephemeris. Accordingly, the TA margin and/or K_offset applied for eachformat representing the satellite ephemeris may be configureddifferently.

As another embodiment of the present disclosure, the base station may beconfigured to indicate that a format used for a serving satellite and aformat used for an upcoming satellite are the same format. That is, itmay be expected that the UE confirms the satellite ephemeris informationreceived through the serving satellite, and that the satellite ephemerisinformation for the upcoming satellite is transmitted in the same formatas previously indicated for the serving satellite.

Hereinafter, a method of signaling and updating satellite ephemerisinformation will be described.

In an embodiment of the present disclosure, a format for displayingsatellite ephemeris based on orbital elements may be used.

For example, when only one satellite ephemeris is used for NTN service,all six element information may be initially stored andprovided/indicated in USIM once or broadcast through SIB 1.

The base station may be configured to provide/indicate the mean anomaly(or true anomaly) indicating the actual position of the satellite foreach epoch (reference) time. Specifically, the base station may beconfigured to update the mean anomaly value for the existing servingsatellite for each epoch (reference) time, and to additionally informthe mean anomaly value for the upcoming satellite for each epoch(reference) time. In this case, the base station may distinguish andconfigure whether the parameter is a value for a serving satellite or avalue for an upcoming satellite.

As another example, it is assumed that a plurality of differentsatellite ephemeris are used for the NTN service.

In this case, six pieces of information about each of the pieces ofephemeris information may be stored in the USIM. For each of thesatellites, it is necessary to indicate which ephemeris among the orbitephemeris stored in the USIM through broadcast information. The basestation may indicate one of indices corresponding to differenttrajectories through a broadcast channel (e.g., SIB1, etc.).

In addition, the base station may update the mean anomaly (or trueanomaly) value for the existing serving satellite for each epoch(reference) time, and may additionally inform the UE of the mean anomaly(or true anomaly) value for the upcoming satellite for each epoch(reference) time. In this case, the base station may distinguish whetherthe parameter is a value for a serving satellite or a value for anupcoming satellite.

As another example, six elements of information about a servingsatellite may be provided during an initial access procedure performedfor the first time. Thereafter, the base station updates the meananomaly (or true anomaly) value for the serving satellite for each epoch(reference) time, and when an upcoming satellite appears, 6 elementinformation about the upcoming satellite may be separately provided. Inaddition, the base station may update the mean anomaly (or true anomaly)value for the upcoming satellite for each epoch (reference) time.

The base station may indicate the size of a specific field(s) of anotherSIB (e.g., SIB_NTN) in SIB1, and actual satellite ephemeris informationmay be broadcast through SIB_NTN. In this case, the base station maybroadcast satellite ephemeris information using not only another SIB(e.g., SIB_NTN) but also dedicated RRC signaling or MAC-CE.

The base station may be configured to inform an mean anomaly (or trueanomaly), which is a parameter value that changes with time, based onthe time served for each country.

And, when the satellite ephemeris information does not changesignificantly, the numerical values of the first 5 elements (half thelength of the major axis, eccentricity, argument of periapsis, longitudeof ascending node, orbit inclination, etc.) among the six orbitalelements generally do not change significantly. Accordingly, when thesatellite ephemeris information is greatly changed or a predefinedupdate period has elapsed, the first five elements may be configured tobe updated.

In another embodiment of the present disclosure, a format for displayingsatellite ephemeris based on an orbit state vector may be used.

For example, it is assumed that only one same satellite ephemeris isused for NTN service.

Based on the serving time for each country, all of the six elementinformation may be initially stored and indicated/configured in the USIMor may be indicated/configured by broadcasting through SIB 1. Ifnecessary, while updating each element related to the existing servingsatellite, the base station may additionally inform the UE of theelement value of each of the upcoming satellites. In this case, the basestation may distinguish whether the parameter is a value for a servingsatellite or a value for an upcoming satellite.

As another example, it is assumed that a plurality of differentsatellite ephemeris are used for the NTN service.

For example, six elements of information for each of a plurality ofephemeris information may be stored in the USIM for a serving time foreach country. The base station may indicate which orbit the satellitefollows from among orbit information stored in the USIM for eachsatellite through broadcast information.

For example, the base station may indicate one of indices correspondingto different trajectories through a broadcast channel. And, ifnecessary, the base station may update each element for the servingsatellite and additionally inform the value of each element for theupcoming satellite. In this case, the base station may distinguishwhether the parameter is a value for a serving satellite or a value foran upcoming satellite.

As another example, in an initial access procedure performed for thefirst time, all six pieces of information about a serving satellite maybe provided for a specific time (e.g., 1/20 of the serving time for eachcountry considering the overhead). Each parameter for the upcomingsatellite may then be updated. Specifically, the position vectorindicated by the first three of the six elements may be updated with along period, and the velocity vector indicated by the remaining threeelements may be updated with a short period. In this case, the UE mayestimate the position of the satellite using the velocity vector updatedin a short period.

Examples of the above-described embodiment may be included as one of theimplementation methods of the present disclosure. In addition, theabove-described embodiments may be implemented independently, but mayalso be implemented in the form of a combination (or combination) ofsome embodiments.

A rule may be defined so that the base station informs the UE of whetherthe above embodiments are applicable (or informs information about therules of the above embodiments) through a predefined signal (e.g., aphysical layer signal or a higher layer signal). The higher layer mayinclude, for example, one or more of functional layers such as MAC, RLC,PDCP, RRC, and SDAP.

Methods or descriptions for implementing the embodiments described inthe present disclosure may be applied separately or one or more methods(or embodiments or descriptions) may be applied in combination. Also,the embodiments described in the present disclosure may be applied to atechnique for estimating an accurate location of a UE.

FIG. 13 is a diagram for describing a signaling procedure according toan embodiment of the present disclosure.

FIG. 13 shows an example of signaling between a network side and aterminal (UE) in a situation in which one or more physicalchannels/signals are transmitted NTN to which embodiments of the presentdisclosure (e.g., each embodiment or a combination of one or more of itsdetailed examples) described above can be applied.

Here, UE/Network side may be an example and may be applied by beingsubstituted with a variety of devices as described in FIG. 14 . FIG. 13is only for convenience of description, but it is not intended to limita scope of the present disclosure. In addition, some step(s) shown inFIG. 13 may be omitted according to a situation and/or a configuration,etc. In addition, in the operation of the network side/UE of FIG. 13 ,the above-described random access procedure operation and the like maybe referred to or used.

In the following description, a Network side may be one base stationincluding a plurality of TRPs or may be one cell including a pluralityof TRPs. Alternatively, the network side may include a plurality ofremote radio heads (RRHs)/remote radio units (RRUs). In an example,ideal/non-ideal backhaul may be configured between TRP 1 and TRP 2included in a Network side. In addition, the following description isdescribed based on a plurality of TRPs, but it may be equally extendedand applied to transmission through a plurality of panels/cells, and mayalso be extended and applied to transmission through a plurality ofRRHs/RRUs.

In addition, although described based on “TRP” in the followingdescription, as described above, “TRP” may be replaced with expressionsof a panel, an antenna array, a cell (e.g., a macro cell/small cell/picocell, etc.), a TP (transmission point), a base station (e.g., gNB,etc.), and the like. As described above, the TRP may be classifiedaccording to information (e.g., CORESET index, ID) on the CORESET group(or CORESET pool). As an example, when one UE is configured to performtransmission/reception with a plurality of TRPs (or cells), this maymean that a plurality of CORESET groups (or CORESET pools) areconfigured for one UE. The configuration of such a CORESET group (orCORESET pool) may be performed through higher layer signaling (e.g., RRCsignaling, etc.).

In addition, the base station may mean a generic term for an object thattransmits and receives data with the UE. For example, the base stationmay be a concept including one or more TPs (Transmission Points), one ormore TRPs (Transmission and Reception Points), and the like. Inaddition, the TP and/or TRP may include a panel of a base station, atransmission and reception unit, and the like.

The UE may receive configuration information and first satelliteephemeris information from the base station (S105).

For example, the configuration information may include NTN-relatedconfiguration information/configuration information for uplinktransmission (e.g., PUCCH-config/PUSCH-config)/reception/HARQprocess-related configuration (e.g., HARQ feedback enable/disable/numberof HARQ processes, etc.)/CSI report-related configuration (e.g., CSIreport configuration/CSI report quantity/CSI-RS resource configuration,etc.) described in the above-described embodiment (e.g., each embodimentor a combination of one or more of its detailed examples).

As another example, the configuration information may includeinformation related to a first validity duration corresponding to afirst satellite and/or information related to a second validity durationcorresponding to a second satellite.

For example, the configuration information may be transmitted throughhigher layer (e.g., RRC or MAC CE) signaling. In addition, the firstsatellite ephemeris information may be transmitted while being includedin the configuration information, but is not limited thereto, and may betransmitted while being included in a separate higher layer signaling.

And, the first satellite ephemeris information may be implemented in afirst ephemeris format based on the position and velocity state vectorof the satellite or/and a second ephemeris format based on one or moreorbit elements.

For example, the operation of the UE (100 or 100 in FIG. 14 ) receivingthe configuration information and the first satellite ephemerisinformation from the base station (200 or 100 in FIG. 14 ) in step S105described above may be implemented by the apparatus of FIG. 14 to bedescribed below. For example, referring to FIG. 14 , one or moreprocessors 102 may control one or more transceivers 106 and/or one ormore memories 104 to receive the configuration information, and thelike, and one or more transceivers 106 may receive the configurationinformation from the network side.

The UE may obtain the first UE-specific TA based on the first satelliteephemeris information (S110). For example, the UE may obtain the firstUE-specific TA by using the first satellite ephemeris information beforethe first validity timer having the first validity duration configuredby the base station expires based on the above-described embodiment(e.g.,, each embodiment or a combination of one or more of its detailedexamples), etc. When the first validity timer expires, the firstsatellite ephemeris information may no longer be valid.

For example, the operation of the UE (100 or 200 in FIG. 14 ) obtainingthe first UE-specific TA in step S110 described above may be implementedby the apparatus of FIG. 14 below. For example, referring to FIG. 14 ,the one or more processors 102 may control the one or more memories 104and the like to obtain the first UE-specific TA.

The UE may transmit the first UE-specific TA to the base station (S115).For example, the UE may report to the base station the first UE-specificTA obtained based on the above-described embodiments (e.g., acombination of one or more of each embodiment or detailed examplesthereof).

For example, the operation of the UE (100 or 200 in FIG. 14 )transmitting the first UE-specific TA in step S115 described above maybe implemented by the apparatus of FIG. 14 below. For example, referringto FIG. 14 , one or more processors 102 may control one or more memories104 and the like to transmit the uplink data/channel.

As mentioned above, the above-described signaling and embodiments of thebase station/UE (e.g., each embodiment or a combination of one or moreof detailed examples thereof) may be implemented by the apparatus to bedescribed with reference to FIG. 14 . For example, the base station maycorrespond to the first device 100 and the UE may correspond to thesecond device 200, and vice versa may be considered in some cases.

For example, the above-described signaling and operation of the basestation/UE (e.g., each embodiment or a combination of one or more of itsdetailed examples) may be processed by one or more processors (e.g.,102, 202) of FIG. 14 , and the above-described signaling and operationof the base station/UE (e.g., each embodiment or a combination of one ormore of its detailed examples) may be stored in the memory (e.g., 104,204) in the form of instructions/programs (e.g. instruction, executablecode) for driving at least one processor (e.g., 102, 202) of FIG. 14 .

General Device to Which the Present Disclosure May be Applied

FIG. 14 illustrates a block diagram of a wireless communicationapparatus according to an embodiment of the present disclosure.

Referring to FIG. 14 , the first device 100 and the second device 200may transmit/receive radio signals through various radio accesstechnologies (e.g., LTE, NR).

A first wireless device 100 may include one or more processors 102 andone or more memories 104 and may additionally include one or moretransceivers 106 and/or one or more antennas 108. A processor 102 maycontrol a memory 104 and/or a transceiver 106 and may be configured toimplement description, functions, procedures, proposals, methods and/oroperation flow charts included in the present disclosure. For example, aprocessor 102 may transmit a wireless signal including firstinformation/signal through a transceiver 106 after generating firstinformation/signal by processing information in a memory 104. Inaddition, a processor 102 may receive a wireless signal including secondinformation/signal through a transceiver 106 and then store informationobtained by signal processing of second information/signal in a memory104. A memory 104 may be connected to a processor 102 and may store avariety of information related to an operation of a processor 102. Forexample, a memory 104 may store a software code including commands forperforming all or part of processes controlled by a processor 102 or forperforming description, functions, procedures, proposals, methods and/oroperation flow charts included in the present disclosure. Here, aprocessor 102 and a memory 104 may be part of a communicationmodem/circuit/chip designed to implement a wireless communicationtechnology (e.g., LTE, NR). A transceiver 106 may be connected to aprocessor 102 and may transmit and/or receive a wireless signal throughone or more antennas 108. A transceiver 106 may include a transmitterand/or a receiver. A transceiver 106 may be used together with a RF(Radio Frequency) unit. In the present disclosure, a wireless device maymean a communication modem/circuit/chip.

A second wireless device 200 may include one or more processors 202 andone or more memories 204 and may additionally include one or moretransceivers 206 and/or one or more antennas 208. A processor 202 maycontrol a memory 204 and/or a transceiver 206 and may be configured toimplement description, functions, procedures, proposals, methods and/oroperation flows charts included in the present disclosure. For example,a processor 202 may generate third information/signal by processinginformation in a memory 204, and then transmit a wireless signalincluding third information/signal through a transceiver 206. Inaddition, a processor 202 may receive a wireless signal including fourthinformation/signal through a transceiver 206, and then store informationobtained by signal processing of fourth information/signal in a memory204. A memory 204 may be connected to a processor 202 and may store avariety of information related to an operation of a processor 202. Forexample, a memory 204 may store a software code including commands forperforming all or part of processes controlled by a processor 202 or forperforming description, functions, procedures, proposals, methods and/oroperation flow charts included in the present disclosure. Here, aprocessor 202 and a memory 204 may be part of a communicationmodem/circuit/chip designed to implement a wireless communicationtechnology (e.g., LTE, NR). A transceiver 206 may be connected to aprocessor 202 and may transmit and/or receive a wireless signal throughone or more antennas 208. A transceiver 206 may include a transmitterand/or a receiver. A transceiver 206 may be used together with a RFunit. In the present disclosure, a wireless device may mean acommunication modem/circuit/chip.

Hereinafter, a hardware element of a wireless device 100, 200 will bedescribed in more detail. It is not limited thereto, but one or moreprotocol layers may be implemented by one or more processors 102, 202.For example, one or more processors 102, 202 may implement one or morelayers (e.g., a functional layer such as PHY, MAC, RLC, PDCP, RRC,SDAP). One or more processors 102, 202 may generate one or more PDUs(Protocol Data Unit) and/or one or more SDUs (Service Data Unit)according to description, functions, procedures, proposals, methodsand/or operation flow charts included in the present disclosure. One ormore processors 102, 202 may generate a message, control information,data or information according to description, functions, procedures,proposals, methods and/or operation flow charts included in the presentdisclosure. One or more processors 102, 202 may generate a signal (e.g.,a baseband signal) including a PDU, a SDU, a message, controlinformation, data or information according to functions, procedures,proposals and/or methods disclosed in the present disclosure to provideit to one or more transceivers 106, 206. One or more processors 102, 202may receive a signal (e.g., a baseband signal) from one or moretransceivers 106, 206 and obtain a PDU, a SDU, a message, controlinformation, data or information according to description, functions,procedures, proposals, methods and/or operation flow charts included inthe present disclosure.

One or more processors 102, 202 may be referred to as a controller, amicro controller, a micro processor or a micro computer. One or moreprocessors 102, 202 may be implemented by a hardware, a firmware, asoftware, or their combination. In an example, one or moreASICs(Application Specific Integrated Circuit), one or more DSPs(DigitalSignal Processor), one or more DSPDs(Digital Signal Processing Device),one or more PLDs(Programmable Logic Device) or one or more FPGAs(FieldProgrammable Gate Arrays) may be included in one or more processors 102,202. Description, functions, procedures, proposals, methods and/oroperation flow charts included in the present disclosure may beimplemented by using a firmware or a software and a firmware or asoftware may be implemented to include a module, a procedure, afunction, etc. A firmware or a software configured to performdescription, functions, procedures, proposals, methods and/or operationflow charts included in the present disclosure may be included in one ormore processors 102, 202 or may be stored in one or more memories 104,204 and driven by one or more processors 102, 202. Description,functions, procedures, proposals, methods and/or operation flow chartsincluded in the present disclosure may be implemented by using afirmware or a software in a form of a code, a command and/or a set ofcommands.

One or more memories 104, 204 may be connected to one or more processors102, 202 and may store data, a signal, a message, information, aprogram, a code, an instruction and/or a command in various forms. Oneor more memories 104, 204 may be configured with ROM, RAM, EPROM, aflash memory, a hard drive, a register, a cash memory, a computerreadable storage medium and/or their combination. One or more memories104, 204 may be positioned inside and/or outside one or more processors102, 202. In addition, one or more memories 104, 204 may be connected toone or more processors 102, 202 through a variety of technologies suchas a wire or wireless connection.

One or more transceivers 106, 206 may transmit user data, controlinformation, a wireless signal/channel, etc. mentioned in methods and/oroperation flow charts, etc. of the present disclosure to one or moreother devices. One or more transceivers 106, 206 may receiver user data,control information, a wireless signal/channel, etc. mentioned indescription, functions, procedures, proposals, methods and/or operationflow charts, etc. included in the present disclosure from one or moreother devices. For example, one or more transceivers 106, 206 may beconnected to one or more processors 102, 202 and may transmit andreceive a wireless signal. For example, one or more processors 102, 202may control one or more transceivers 106, 206 to transmit user data,control information or a wireless signal to one or more other devices.In addition, one or more processors 102, 202 may control one or moretransceivers 106, 206 to receive user data, control information or awireless signal from one or more other devices. In addition, one or moretransceivers 106, 206 may be connected to one or more antennas 108, 208and one or more transceivers 106, 206 may be configured to transmit andreceive user data, control information, a wireless signal/channel, etc.mentioned in description, functions, procedures, proposals, methodsand/or operation flow charts, etc. included in the present disclosurethrough one or more antennas 108, 208. In the present disclosure, one ormore antennas may be a plurality of physical antennas or a plurality oflogical antennas (e.g., an antenna port). One or more transceivers 106,206 may convert a received wireless signal/channel, etc. into a basebandsignal from a RF band signal to process received user data, controlinformation, wireless signal/channel, etc. by using one or moreprocessors 102, 202. One or more transceivers 106, 206 may convert userdata, control information, a wireless signal/channel, etc. which areprocessed by using one or more processors 102, 202 from a basebandsignal to a RF band signal. Therefor, one or more transceivers 106, 206may include an (analogue) oscillator and/or a filter.

Embodiments described above are that elements and features of thepresent disclosure are combined in a predetermined form. Each element orfeature should be considered to be optional unless otherwise explicitlymentioned. Each element or feature may be implemented in a form that itis not combined with other element or feature. In addition, anembodiment of the present disclosure may include combining a part ofelements and/or features. An order of operations described inembodiments of the present disclosure may be changed. Some elements orfeatures of one embodiment may be included in other embodiment or may besubstituted with a corresponding element or a feature of otherembodiment. It is clear that an embodiment may include combining claimswithout an explicit dependency relationship in claims or may be includedas a new claim by amendment after application.

It is clear to a person skilled in the pertinent art that the presentdisclosure may be implemented in other specific form in a scope notgoing beyond an essential feature of the present disclosure.Accordingly, the above-described detailed description should not berestrictively construed in every aspect and should be considered to beillustrative. A scope of the present disclosure should be determined byreasonable construction of an attached claim and all changes within anequivalent scope of the present disclosure are included in a scope ofthe present disclosure.

A scope of the present disclosure includes software ormachine-executable commands (e.g., an operating system, an application,a firmware, a program, etc.) which execute an operation according to amethod of various embodiments in a device or a computer and anon-transitory computer-readable medium that such a software or acommand, etc. are stored and are executable in a device or a computer. Acommand which may be used to program a processing system performing afeature described in the present disclosure may be stored in a storagemedium or a computer-readable storage medium and a feature described inthe present disclosure may be implemented by using a computer programproduct including such a storage medium. A storage medium may include ahigh-speed random-access memory such as DRAM, SRAM, DDR RAM or otherrandom-access solid state memory device, but it is not limited thereto,and it may include a nonvolatile memory such as one or more magneticdisk storage devices, optical disk storage devices, flash memory devicesor other nonvolatile solid state storage devices. A memory optionallyincludes one or more storage devices positioned remotely fromprocessor(s). A memory or alternatively, nonvolatile memory device(s) ina memory include a non-transitory computer-readable storage medium. Afeature described in the present disclosure may be stored in any one ofmachine-readable mediums to control a hardware of a processing systemand may be integrated into a software and/or a firmware which allows aprocessing system to interact with other mechanism utilizing a resultfrom an embodiment of the present disclosure. Such a software or afirmware may include an application code, a device driver, an operatingsystem and an execution environment/container, but it is not limitedthereto.

Here, a wireless communication technology implemented in a wirelessdevice 100, 200 of the present disclosure may include NarrowbandInternet of Things for a low-power communication as well as LTE, NR and6G. Here, for example, an NB-IoT technology may be an example of aLPWAN(Low Power Wide Area Network) technology, may be implemented in astandard of LTE Cat NB1 and/or LTE Cat NB2, etc. and is not limited tothe above-described name. Additionally or alternatively, a wirelesscommunication technology implemented in a wireless device 100, 200 ofthe present disclosure may perform a communication based on a LTE-Mtechnology. Here, in an example, a LTE-M technology may be an example ofa LPWAN technology and may be referred to a variety of names such as aneMTC (enhanced Machine Type Communication), etc. For example, an LTE-Mtechnology may be implemented in at least any one of various standardsincluding 1) LTE CAT 0, 2) LTE Cat 51, 3) LTE Cat M2, 4) LTEnon-BL(non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine TypeCommunication, and/or 7) LTE M and so on and it is not limited to theabove-described name. Additionally or alternatively, a wirelesscommunication technology implemented in a wireless device 100, 200 ofthe present disclosure may include at least any one of a ZigBee, aBluetooth and a low power wide area network (LPWAN) considering alow-power communication and it is not limited to the above-describedname. In an example, a ZigBee technology may generate PAN(personal areanetworks) related to a small/low-power digital communication based on avariety of standards such as IEEE 802.15.4, etc. and may be referred toas a variety of names.

A method proposed by the present disclosure is mainly described based onan example applied to 3GPP LTE/LTE-A, 5G system, but may be applied tovarious wireless communication systems other than the 3GPP LTE/LTE-A, 5Gsystem.

What is claimed is:
 1. A method performed by a user equipment (UE) in awireless communication system, the method comprising: receiving firstsatellite ephemeris information related to a first satellite andinformation related to a first validity duration during which the UE canapply the first satellite ephemeris information; starting a validitytimer with a timer value set to the first validity duration; and basedon the information related to a second validity duration during whichthe UE can apply second satellite ephemeris information being received,restarting the validity timer with the timer value set to the secondvalidity duration, wherein the UE obtains a first timing advance (TA)for the first satellite based on the first satellite ephemerisinformation related to the first validity duration, before acquiring thesecond satellite ephemeris information, and wherein the UE obtains asecond TA for the first satellite based on the second satelliteephemeris information related to the second validity duration.
 2. Themethod of claim 1, wherein: the satellite ephemeris information is basedon at least one of a first ephemeris format or a second ephemerisformat, the first ephemeris format is based on at least one of aposition state vector or a velocity state vector of a satellite, and thesecond ephemeris format is based on at least one orbit element.
 3. Themethod of claim 1, wherein: based on the information related to thesecond validity duration being not received within the first validityduration and based on expiration of the validity timer, the firstsatellite ephemeris information is no longer valid for TA obtainment ofthe UE.
 4. The method of claim 1, wherein: the first satellite is aserving satellite and the second satellite is a neighbour satellite. 5.The method of claim 4, wherein: a validity duration corresponding to thefirst satellite and a validity duration corresponding to the secondsatellite are independently configured.
 6. The method of claim 1,wherein: the wireless communication system is a non-terrestrial network(NTN) system.
 7. The method of claim 1, wherein: the first satelliteephemeris information and the information related to the first validityduration is included in a higher-layer signaling.
 8. A user equipment(UE) configured to operate in a wireless communication system, the UEcomprising: at least one transceiver; at least one processor connectedto the at least one transceiver; and at least one memory connected tothe at least one processor and storing instructions that, based on beingexecuted by the at least one processor, perform operations comprising:receiving, through the at least one transceiver, first satelliteephemeris information related to a first satellite and informationrelated to a first validity duration during which the UE can apply thefirst satellite ephemeris information; starting a validity timer with atimer value set to the first validity duration; and based on theinformation related to a second validity duration during which the UEcan apply second satellite ephemeris information being received,restarting the validity timer with the timer value set to the secondvalidity duration, wherein the UE obtains a first timing advance (TA)for the first satellite based on the first satellite ephemerisinformation related to the first validity duration, before acquiring thesecond satellite ephemeris information, and wherein the UE obtains asecond TA for the first satellite based on the second satelliteephemeris information related to the second validity duration.